Cleats are used in many applications where it is necessary to secure lines or ropes. In small boat sailing, a particular type of cleat is commonly used to secure the jib sheet and main-sheet. In these applications, the cleat has traditionally permitted the lines to move in one direction while preventing movement in the other direction. A locking cleat or mooring plate will not suffice because they do not permit the sailor to draw rapidly in the lines, as is needed for continual adjustment of sail trim, nor to release the lines quickly enough to prevent capsize.
Conventionally, the solution to this problem has been to use what is commonly referred to as a pivoting cam cleat. For example, typical cam cleats of various designs are shown in U.S. Letters Pat. Nos. 3,265,032 issued Aug. 9, 1966; 3,730,129 issued May 1, 1973; and 4,084,532 issued Apr. 18, 1978. Essentially a cam cleat comprises a pair of spring-biased cam elements, or a single spring-biased cam element and an abutment that cooperate with each other to receive a line therebetween. The eccentricity of the cams is such that drawing a line in one direction causes the gap between the elements to widen and thus, the line to draw smoothly, while drawing the line in the opposite direction allows the gap to close and the line to be secured.
When a conventional cam cleat is used, difficulties are sometimes encountered, because, in order to release a locked line, a sailor must pull opposite the force exerted by the wind on the sail. Once the gap between the cam elements has been widened sufficiently by drawing in the line, the sailor may lift the line from the cleat and manually release it. However, in a strong wind, this task can be difficult to perform in time to prevent capsize. Another problem with conventional cam cleats occurs when the springs weaken or stick as a result of corrosion or salt. In these instances where the cams do not pivot freely, the cam cleat may not "lock" on the line unless it is closed manually.
Additionally, cam cleats suffer the deficiency of having no means to permit a limited release of line when a certain line tension is exceeded. Such a feature would obviously be of value in counteracting the sudden gusts of wind that sometimes cause even the experienced sailor to heel dangerously and the inexperienced sailor to capsize.